ReviewExercise and oxidative stress: Potential effects of antioxidant dietary strategies in sports
Introduction
Oxidative stress reflects an imbalance between production of reactive oxygen species (ROS) and the ability to detoxify reactive intermediates or to repair the resulting damage by an adequate antioxidant defense. This adverse condition may lead to damage of all cellular components, including proteins, lipids, carbohydrates, and nucleic acids [1]. Oxidative stress is recognized to be involved in many physiological conditions (e.g., aging and exercise) and diseases (including inflammation, cardiovascular and neurodegenerative diseases, and cancer) [1]. In particular, the effect of exercise on redox balance is extremely complex, depending on age, sex, and training level, as well as intensity and duration of exercise. Although regular moderate training appears beneficial for oxidative stress and health, acute and strenuous bouts of aerobic and anaerobic exercise can induce ROS overproduction. Nonetheless, although exercise leads to increased oxidative stress, the same exercise stimulus appears necessary to allow an up-regulation in endogenous antioxidant defenses according to the hormesis theory (Fig. 1). Specifically, this hypothesis suggests that the organism’s reaction to repeated increases in ROS production via exercise bouts involves adaptive mechanisms. In particular, hormesis elicits an antioxidant up-regulation, a shift toward a more reducing environment, induction of increased stress resistance, ultimately leading to an enhanced life span [2]. Same adaptative responses and the detoxifying function of antioxidant enzymes (superoxide dismutase [SOD], catalase [CAT], glutathione peroxidase [GPx], glutathione reductase, glutathione-S-transferase) and nonenzymatic antioxidants (such as vitamins E, A, C; glutathione [GSH]; and uric acid) take part in the prevention of excessive oxidative stress related to performance enhancement, aging prevention, and pathological risk in professional athletes [2].
In recent years, the consumption of supplemental antioxidants in athletes has increased enormously despite the unclear evidence of their benefit. The delicate balance between oxidants and antioxidants may be counterbalanced by an adequate dietary/supplemental antioxidant intake (extrinsic factor). In particular, exogenous supplemental antioxidants have received interest as a noninvasive tool useful in decreasing muscle damage and improving exercise performance and in preventing or reducing oxidative stress, improving life span and performance, and lowering specific risks for pathologic outcomes that strenuous exercise produces in athletes [3], [4]. Nonetheless, the revision of available information has evidenced a lack of consistent data regarding exogenous antioxidant supplementation effects on physiological parameters, with most studies reporting no or negative effects on these end points [3], [4]. Moreover, some studies suggest adverse effects of antioxidant supplementation on the health and performance of exercise-trained individuals [3], [4]. In particular, a too-low oxidative stress status may be detrimental and may blunt positive responses related to hormesis because ROS retain key roles as regulatory mediators in signaling processes essential to the correct functioning of cells. Conversely, high doses of antioxidants may negatively affect important ROS-mediated physiological processes because they may shift from antioxidant capacity to prooxidant effects.
At present, few studies if any approach this topic from a whole food or dietary perspective [5], [6], [7], [8], [9]. An adequate intake of vitamins and minerals, and the use of natural foods that are rich in antioxidants (fruits, vegetables, etc.) through a varied and balanced diet rich in fruits, fiber, and vegetables could represent the ideal approach to maintaining the optimal antioxidant status as antioxidants are present in natural ratios and proportions, which may act in synergy to optimize the antioxidant effect. The Mediterranean diet could be a suitable candidate, although data in this field are still scarce. In this review, evidence on the relationship between exercise and oxidative stress and potential effects of dietary strategies in athletes are discussed. The differences between diet and exogenous supplementation as well as available tools to estimate effectiveness of antioxidant intake are also reported.
Section snippets
Available biomarkers to estimate oxidative stress status
The measurement of the oxidative stress in vivo is difficult due to the extreme complexity of the antioxidant/oxidant network and the very short half-life of free radicals [2]. Generally, indirect biomarkers are measured, such as conjugated dienes, hydroperoxides, malondialdehyde, 4-hydroxynonenal, hydrocarbons such as pentane and ethane (in breath), F2-isoprostanes, and oxidized low-density lipoprotein [1], [2]. Conversely, total antioxidant capacity [TAC] can be estimated in biological fluids
Effects of exercise on oxidative stress and health
At rest, oxidative stress status is generally found to be lower in athletes than in sedentary individuals, although it also has been observed increased or unchanged [11], [12]. Many variables clearly affect these results, two of the most important being differences in experimental design (e.g., exercise intensities) and different methods used to estimate oxidative stress status. Several studies showed a lower oxidative response in athletes than in controls both at rest and soon after exercise,
Dietary versus supplemental antioxidants: same effectiveness?
In the past, antioxidant supplementation was expected to be effective against cumulative effects of strenuous exercise–induced free radical damage to heart and skeletal muscle [21]. Vitamin C at various dosages, administered alone or in combination with other antioxidants, chronically or acutely, is the most frequently used antioxidant in human and experimental studies, although with discordant results on its protective role [22]. One of the key determinants for these differences is the dose
Dietary strategies and oxidative stress in athletes
Most studies concerning the area of recovery from exercise in athletes focus on the use of nutritional supplements rather than on foods [2]. The study of the effects of natural food is difficult because food products are difficult to group according to the type and content of antioxidants. Nonetheless, the protective effect of a diet containing natural sources of antioxidants is probably not equivalent to the protective effect of supplementation. Whole foods, rather than capsules, contain
Conclusions
The interrelationship of exercise and oxidative stress remains extremely complex, depending on the mode, intensity, and duration of exercise, and individual susceptibility to oxidative stress injury determined by genetic and lifestyle factors.
At present, interpretation of available results remains difficult due to the variety of physiological networks involved, and differences in biomarkers and methods used as well as in nutritional composition of foods. The development of integrative panels
Acknowledgment
The authors acknowledge Rossella Pucci for her graphical contribution to Figure 3.
References (61)
- et al.
Free radicals and antioxidants in normal physiological functions and human disease
Int J Biochem Cell Biol
(2007) - et al.
Blood oxidative stress biomarkers: influence of sex, exercise training status, and dietary intake
Gend Med
(2008) - et al.
Systemic adaptation to oxidative challenge induced by regular exercise
Free Radic Biol Med
(2008) - et al.
Oral administration of vitamin C decreases muscle mitochondrial biogenesis and hampers training-induced adaptations in endurance performance
Am J Clin Nutr
(2008) - et al.
Organic grape juice intake improves functional capillary density and postocclusive reactive hyperemia in triathletes
Clinics
(2011) Exercise training and the antioxidant alpha-lipoic acid in the treatment of insulin resistance and type 2 diabetes
Free Radic Biol Med
(2006)- et al.
Coenzyme Q10 supplementation and exercise-induced oxidative stress in humans
Nutrition
(2012) - et al.
Vitamin E and its function in membranes
Prog Lipid Res
(1999) - et al.
Effects of the Mediterranean diet on longevity and age-related morbid conditions
Maturitas
(2009) - et al.
Mediterranean diet and red wine protect against oxidative damage in young volunteers
Atherosclerosis
(2010)
Biomarkers to estimate bioefficacy of dietary/supplemental antioxidants in sports
Antioxidant supplementation during exercise training: Beneficial or detrimental?
Sports Med
Vitamin supplementation benefits in master athletes
Sports Med
Vitamins C and E for asthma and exercise-induced bronchoconstriction
Cochrane Database Syst Rev
Polyphenol supplementation: benefits for exercise performance or oxidative stress?
Sports Med
Vitamin C for asthma and exercise-induced bronchoconstriction
Cochrane Database Syst Rev
Exploring the role of genetic variability and lifestyle in oxidative stress response for healthy aging and longevity
Int J Mol Sci
Free radicals and sprint exercise in humans
Free Radic Res
An easy and reliable automated method to estimate oxidative stress in the clinical setting
Methods Mol Biol
Differential impact of acute bout of exercise on redox- and oxidative damage-related profiles between untrained subjects and amateur runners
Physiol Res
Determination of nitrite plus nitrate and malondialdehyde in human plasma: analytical performance and the effect of smoking and exercise
Clin Chem Lab Med
Antioxidant status and lipid peroxidation after short-term maximal exercise in trained and untrained humans
Am J Phys
Antioxidant status of interval-trained athletes in various sports
Int J Sports Med
Endurance training attenuates exercise-induced oxidative stress in erythrocytes in rat
Eur J Appl Physiol
Innovative approach to interpret the variability of biomarkers after ultra-endurance exercise: the multifactorial analysis.
Biomark Med
Physical activity and all-cause mortality: what is the dose-response relation?
Med Sci Sports Exerc
Is physical activity able to modify oxidative damage in cardiovascular aging?
Oxid Med Cell Longev
Normal adaptations to exercise despite protection against oxidative stress
Am J Physiol Endocrinol Metab
Effects of dietary antioxidants on training and performance in female runners
Eur J Sport Sci
Authors' perspective: what is the optimum intake of vitamin C in humans?
Crit Rev Food Sci Nutr
Cited by (303)
The NRF2/Keap1 pathway as a therapeutic target in inflammatory bowel disease
2023, Trends in Molecular MedicinePolygonati rhizoma polysaccharides relieve exercise-induced fatigue by regulating gut microbiota
2023, Journal of Functional FoodsAssociation between healthy dietary patterns and markers of oxidative stress in the Sister Study
2024, European Journal of Nutrition
All authors have read and approved the final manuscript version. The authors have no conflicts of interest to disclose.